First, you replied to a 9 year old message. That's not generally considered good form!

That said, there's a setting on the "Operations" tab in Service Center that you can uncheck to hide messages from the extension, but I'm not sure whether it also hides the SLOWEXTENSION warnings. It may be that unchecking the checbox at the consuming eSpace will work.

If that checkbox doesn't work, a solution could be to sleep a short while multiple times. So call the Sleep 10 times with 100ms. That'll keep it under the radar of the Platform, but will amount to the same.